title: Chemical analysis of nickel-titanium rotary instruments with and without electropolishing after cleaning procedures with sodium hypochlorite.
abstract: The aim of this study was to chemically analyze rotary nickel-titanium instruments with and without electropolishing after cleaning procedures with NaOCl. To evaluate the effect of 5.25% NaOCl on electropolished RaCe instruments, a total of 18 instruments were tested. A control group of 18 nonelectropolished RaCe instruments was used. The surface of each instrument was analyzed before and after cleaning in NaOCl by using energy dispersive x-ray analysis, Auger electron spectroscopy, and scanning electron microscopy. Surface defects were recorded, and a chi(2) test was used for statistical analysis. After immersion in NaOCl, the nonelectropolished and electropolished files showed a significant increase of iron deposits as a result of galvanic corrosion of the shaft (P < .05). The nonelectropolished files showed marked presence of NaCl deposits in the machining marks and microcracks. As regards the chemical nature of the surface, the electropolished files had an oxide increase compared with the low oxide concentration (mainly TiO2) before cleaning. The nonelectropolished files already possessed higher oxides concentration (TiO2 and NiO) before NaOCl cleaning. NaOCl treatment affects the chemical composition of the surface and, in particular for nonelectropolished instruments, of the bulk exposed through machining marks and fabrication microcracks.
authors.affiliation: Private practice, Catania, Italy. Electronic address: endomaterials@fastwebnet.it.
authors.forename: Antonio
authors.initials: A
authors.lastname: Bonaccorso
authors.affiliation: Department of Operative Dentistry, University of Münster, Münster, Germany.
authors.forename: Edgar
authors.initials: E
authors.lastname: Schäfer
authors.affiliation: Department of Chemical Science, University of Catania, Catania, Sicily, Italy.
authors.forename: Guglielmo Guido
authors.initials: GG
authors.lastname: Condorelli
authors.affiliation: Faculty of Dentistry, University of Verona, Verona, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cantatore
authors.affiliation: Faculty of Dentistry, University of Catania, Catania, Sicily, Italy.
authors.forename: Teresa Roberta
authors.initials: TR
authors.lastname: Tripi
mesh_terms: D003343:Corrosion; D003666:Decontamination; D003722:Dental Alloys / Q000737:chemistry; D019551:Dental Disinfectants / Q000737:chemistry*; D003762:Dental Instruments; D003775:Dental Polishing; D055664:Electrochemical Techniques; D004577:Electron Probe Microanalysis; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry; D010087:Oxides / Q000032:analysis; D011897:Random Allocation; D018915:Root Canal Preparation / Q000295:instrumentation*; D012965:Sodium Chloride / Q000032:analysis; D012973:Sodium Hypochlorite / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D003722:Dental Alloys; D019551:Dental Disinfectants; D010087:Oxides; C040654:titanium nickelide; D012965:Sodium Chloride; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite